1. Technical Field
The invention relates to a contour resonator in which a plurality of vibrating substrates are laminated and bonded.
2. Related Art
As piezoelectric resonators for portable apparatuses, information and communication apparatuses and measurement apparatuses, thickness shear resonators such as AT cut quartz crystal resonators and contour mode resonators such as DT cut quartz crystal resonators (contour shear quartz crystal resonators), Lame-mode quartz crystal resonators and pseudo-Lame-mode quartz crystal resonators. In “Lame-mode Quartz Crystal Resonator Formed by Etching Method”, Hirofumi Kawashima and Masaru Matsuyama, 24th EM Symposium, pp. 11 to 16 (a first example of related art); and “Development of Small-sized Lame-mode Quartz Crystal Resonator”, Masaya Mizumoto, Masashi Akino, Takashi Nishizuka, Hidenori Ashizawa, Masahide Marumo and Masato Amamiya, 35th EM Symposium, pp. 31 to 34 (a second example of related art), a Lame-mode quartz crystal resonator in which excitation electrodes are formed on the both surfaces of a rectangular quartz crystal substrate has been reported.
It has been shown that, between two facing sides of a quartz crystal substrate, excited are Lame-mode vibrations in which a distance between one two sides and a distance between the other two sides orthogonal thereto alternately expand and contract.
Disclosed in JP-A-2005-26843 is a Lame-mode quartz crystal resonator using a quartz crystal substrate for which θ is 40° to 50°, φ is −40° to −60° (that is, φ is 120° to 140°) or φ is 40° to 60° in the expression of cut angle represented as YXltφ/θ of IRE (abbreviation of Institute of Radio Engineers, now IEEE) standards.
Disclosed in JP-A-52-149084 is a GT-cut quartz crystal resonator in which θ is 40° to 50°. JP-A-2001-313537 and “Extensional Vibrations of Rectangular Crystal Plates”, P. C. Y Lee, et al., Proc. 35th Ann. Freq. Control Symposium (1981) (a third example of related art) disclose that a ratio of sides of a GT-cut quartz crystal resonator of θ=45° is set to 1, so that a Lame-mode quartz crystal resonator is achieved.
In JP-A-08-031758, a contour shear quartz crystal resonator is disclosed.
In such contour resonators, excitation electrodes are formed on both front and back sides of a single-layer quartz crystal substrate.
Here, reducing the distance between excitation electrodes on front and back sides (that is, reducing the thickness of a quartz crystal substrate) can increase the electric field efficiency to achieve a low-loss contour resonator.
However, there is a problem in that as the thickness of a quartz crystal substrate is reduced, the quartz crystal substrate is lacking in the structural strength including the support structure and therefore cannot endure the practical use.